Cutting, compulsive skin picking (CSP) and scratching (not from itchiness), and hair pulling (trichotillomania) may in many cases be more a sensory processing issue than a psychological condition related to body dysmorphia, depression, or compulsions. All these conditions provide intense deep skin sensation to balance out the nervous system, in the same way that the autistic child will bang her head against the wall and endlessly flap her arms.

Information taken from Uptight & Off Center.